1. Field of the Invention
This invention relates to ski boot bindings, and in particular to a binding for the heel of a touring ski boot.
2. Prior Art
Ski touring, or cross-country skiing, involves travelling on snow using very light weight, narrow skis. Suitable terrain for this type of skiing is less steep than most alpine, or downhill ski courses, and involves climbing, walking on level terrain and, inevitably, skiing down moderate slopes. Skis used for touring are long, narrow and of very light construction usually of either laminated wood or fiberglass. Touring boots are lightweight and low cut and have a very flexible sole to allow the boot heel to be raised freely while walking or gliding on the skis. Conventional touring ski boot bindings (of which there are several well known types) attach only the toe of the boot to the ski to allow this.
Touring or cross-country ski boots and ski bindings are markedly different from alpine or downhill ski boots and ski bindings. As noted, touring ski boots are comfortable and light-weight with soft flexible uppers and flexible soles that are normally attached to the ski at the toe end only. Alpine ski boots are heavy rigid affairs with thick inflexible soles that are attached to the skis at both front and rear ends. Touring ski bindings normally secure the toe only of the ski boot to the ski, and these toe bindings do not have a safety release feature and must be released by hand. Alpine ski bindings have built-in safety release features which automatically release the ski boot in the event of an accident while skiing.
Touring ski boot toe bindings serve their intended purpose very well in that they permit the skier to move on his skis with a natural walking motion uphill, on the level and down small slopes. However, these touring ski bindings do not provide adequate control of the skis when sliding down hill on steeper slopes. That is to say, due to the softness of the touring boot and the flexibility of the sole, the heel of the boot has very little lateral stability when the skier is standing on the ski and sliding downhill. In order to provide the desired control for downhill skiing the ski boot should somehow be immobilized and/or attached to the ski at the heel.
One known procedure for improving the lateral stability of the heel of the boot on the ski involves attaching a plate with raised, serrated edges to the ski under the heel of the boot to hold the latter in place when the heel is weighted. However, serrated heel plates do not provide a positive anchoring of the boot heel, and excessive lateral heel movement makes turning the touring ski difficult. Another known procedure involves the use of a cable that extends around the heel of the boot to either the toe binding or to a lever positioned on the ski in front of the toe binding. The cable bindings used on touring skis are designed primarily to maintain the boot in the toe binding while allowing the heel to be raised freely. Placement of cable guiding lugs along the sides of the ski between the toe and the heel will permit a degree of positive hold-down of the boot heel, but due to the soft sole construction of the touring boot, a compression and buckling of the boot sole may result, thus limiting the allowable hold-down force. In practice cable bindings used in this manner do not provide the desired heel stability for turning touring skis. In the event of a forwards fall, cable bindings are incapable of safety-release, which usually results in a broken ski.
Both heel retaining forces for downhill skiing on touring skis are much less than that required for alpine equipment. Nonetheless, some degree of vertical hold down and high lateral stability of the boot heel should be provided when skiing downhill. The vertical hold down of the boot heel may be of the positive type (that is, non-releasable except intentionally by the skier), or it may be of the safety release type that releases automatically when heel stresses on the binding exceed a predetermined value (as when a ski tip goes under the snow or the skier accidently falls). Of course, when walking or gliding on the skis a touring ski heel binding should allow unobstructed vertical motion of the heel. Accordingly, after an intensive investigation of these and related problems involved in providing satisfactory control of touring skis on downhill slopes, we have developed a novel binding for the heels of touring ski boots that is light in weight, reliable in operation, and readily engaged or disengaged by the skier without in any way affecting the function or security of the separate toe binding of the touring ski.